An important task in the field of materials for space applications is the study of the influence of outer space factors on polymer composite materials (PCM). During the last two decades, the stability of these materials in outer space conditions (by exposing them on the outside of the Salyut and Mir orbital stations) under a long term program at the M.V. Khrunitchev State Space Scientific Production Center ("Salyut "Design Bureau) is studied after returning them to the Earth. Over years of flight experiments, the exposure of a wide class of PCM for 102, 304, 382, 456, 686, 1024 and 1501 days at "Salyut" and "Mir" orbital stations was carried out. Objects of the research were KMU-2, KMU-31, KMU-41 carbon fiber reinforced plastics, VPS-7V glass fiber reinforced plastic and also their compounds with different variants of surface protection from the direct influence of natural factors: aluminium foil, aluminium alloy, glass netting, lacquer and paint coating. With the help of various physical methods the influence of coatings and screens upon the complex of mechanical, diffusion, heat-physical parameters of monoplastics and hybrid systems was investigated. From the electronic microscopy and diffusion analysis data the destruction and microerosion effects of materials' surfaces exposured to the space without protection were estimated. It has been shown that a consequence of damage of PCM's surfaces is the rough rise in diffusion coefficient, decrease of the microhardness and dynamic shear modulus parameters of the unprotected samples. The mentioned effects are significantly weakened under shielding of open plastics' surfaces by aluminium foil or by a layer of another plastic. Special attention was paid to the research of KMU-31 carbon fiber reinforced plastic with a thin layer of glass fiber cloth used as a covering for panels for micrometeoroid protection of the Mir orbital complex, exposed for 1024 days under the layer of same material. It has been shown that the protected plastic is completely shielded from destruction. At that, changes in physical properties are determined by postcuring processes and improvement of structural homogeneity of epoxy binders. The consequence is increase in dynamic shear modulus at raised temperatures and also in heat-resistance of the composites after 300-500 days of exposure to the space. Basis on the obtained results, the substantiation of service stability for composite materials used for micrometeoroid protection of the "Mir" orbital complex under vacuum skin was given. Models of physical aging processes of PCM with different variants of protection were worked out and a forecast in the change of basic operation parameters for 15 years in the space was given.
